From Chapter 3 of Rachel Carson's seminal book, Silent Spring (1962):

FOR THE FIRST TIME in the history of the world, every human being is now subjected to contact with dangerous chemicals, from the moment of conception until death. In the less than two decades of their use, the synthetic pesticides have been so thoroughly distributed throughout the animate and inanimate world that they occur virtually everywhere. They have been recovered from most of the major river systems and even from streams of groundwater flowing unseen through the earth. Residues of these chemicals linger in soil to which they may have been applied a dozen years before. They have entered and lodged in the bodies of fish, birds, reptiles, and domestic and wild animals so universally that scientists carrying on animal experiments find it almost impossible to locate subjects free from such contamination. They have been found in fish in remote mountain lakes, in earthworms burrowing in soil, in the eggs of birds—and in man himself.

So, is it almost impossible for scientists to find animals that are not contaminated by chemicals? (By chemicals, Carson generally means insecticides and pesticides.) Has the natural ecological cycle spread synthetic chemicals to all corners of the planet?

Carson also goes on to say that:

They occur in the mother’s milk, and probably in the tissues of the unborn child.

Is there evidence to suggest that breast milk is also now similarly contaminated? In most women around the world?

  • I realise that the book is from 1962. But it is still cited often and the claims don't sound terribly dated either.
    – user7920
    Nov 28, 2014 at 20:16
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    You should probably make the clarification of "insecticides and pesticides" a bit more prominent. It is by definition impossible to find Earth-based life that is uncontaminated by chemicals.
    – Mark
    Nov 28, 2014 at 21:45
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    The word "contaminated" here is loaded. Just because a substance is detectable in animal tissue does not imply that it is actually causing a problem for that animal (or any other animal that eats it). Actually, given sufficiently sensitive tests this claim is not surprising at all. Nov 29, 2014 at 17:21
  • @NateEldredge There's nothing that says that a contaminant needs to be harmful. But insecticides and pesticides are substances that are both foreign and, I dare say, unwelcome in human and animal tissue. And regardless of how sensitive the test is, I would be astounded to discover that a species of army ant in a pristine part of the Amazon rainforest has insecticides/pesticides in its system.
    – user7920
    Dec 2, 2014 at 20:38
  • @coleopterist: Really? I'd be astounded if it doesn't. Have you ever seen the homework problem that goes something like this? "Take a deep breath. Estimate the probability that you just inhaled a molecule of air that was exhaled by Julius Caesar with his dying breath." It turns out to be overwhelmingly close to 1. (Basically, Avogadro's number is bigger than you think.) I would think it's extremely likely that such an insect contains at least some molecules of any pesticide ever made, which a sufficiently sensitive test could in principle detect. Dec 2, 2014 at 21:26

2 Answers 2


Wikipedia says,

Silent Spring was met with fierce opposition by chemical companies, but it spurred a reversal in national pesticide policy, led to a nationwide ban on DDT for agricultural uses,[2] and inspired an environmental movement that led to the creation of the U.S. Environmental Protection Agency.[3][4]

Has the natural ecological cycle spread synthetic chemicals to all corners of the planet?

Insects are low on the food chain.

So you get articles like Significance of the Food Chain in DDT Accumulation by Fish which say,

Brook trout accumulated approximately 10 times more of the available DDT from the food than directly from the water. Since, in aquatic environments, the concentration of DDT is usually much higher in the food chain than in the water, we suggest that the food chain is the major source of DDT for fish in natural waters.

And PCBS, DDE, DDT, and TCDD-EQ in two species of albatross on Sand Island, Midway Atoll, North Pacific Ocean

Concentrations of total polychlorinated biphenyls (PCBs) and organochlorine insecticides, including the 1 1,1-trichloro-2, 2′-bis-p-chlorophenyl-ethane (DDT) complex, were measured in the plasma of chicks and adults and in eggs of Laysan albatrosses (Diomedea immutabilis) and black-footed albatrosses (Diomedea nigripes) in a remote area of the central North Pacific Ocean.

Is there evidence to suggest that breast milk is also now similarly contaminated? In most women around the world?

Worldwide trends in DDT levels in human breast milk (whose abstract is here) shows DDT being detected in "Other Regions" which include Papua New Guinea and Kenya; as well as in diverse other countries, in North America, Latin America, Eastern and Western Europe, the Middle East, and Asia,


You are presenting two claims in your question, please split it up appropriately. I will hereby address your second claim. Research from 1986 to 1997 indeed confirms that some pesticides and insecticides can indeed be found in breast milk:

Between summer 1995 and summer 1997 the median PCB concentration level was 0.502 mg/kg, the median DDT level 0.202 mg/kg, the median HCB level 0.065 mg/kg and the median β-HCH level 0.036 mg/kg, all values expressed on a fat basis.

Now technically some of these chemicals can be used for different things then pesticides and insecticides as well, that's their most common usage and would explain their presence in breast milk.

I am not going to make a judgement call how bad these (relatively small) amounts realistically are, though

Higher HCB and β-HCH concentration levels were associated with lower birth weights of female infants.

But the good news is that:

The median concentration levels decreased by 80–90% during the past 12 years and the median PCB levels by 60%.

Cursory browsing through other research seems to confirm the presence of these chemicals in breast milk as well.

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